The present invention relates to a variable control screening apparatus, and more particularly, to a vibrating screen used to separate and sort multiple size solids and particulates.
Vibrating screen arrangements have been in use for many years in gravel and rock quarrying for screening and/or for dewatering wet material. Generally, the arrangements comprise a working member mounted on a frame and an exciter arranged to impart vibrating motion to the member. The working member is fitted with a screen deck with a conventionally rigid aperture element which may be made up of a plurality of screening panels.
Despite the fact that the working member is vibrated in use, blinding of the apertures often occurs. When blinding occurs, separation of particulars become less uniform and less efficient. It is therefore an object of this invention to reduce blinding and improve efficiency.
Vibrating screening decks have also been widely in use in the past for separating particles of various sizes and composition. Such screening deck typically comprise a rectangular frame suspended in operation with screen cloth mounted within the frame from which the materials are separated. The frame and screen in such decks are suspended at an angle. The entire frame is vibrated, thus imparting vibration to the machine which in turn causes the solids to move down the screen. As the materials move down the vibrating screen, the solids of smaller mesh size pass through the screen with larger solids discharged from the lower end of the screen.
One disadvantage of such prior screening devices is the substantial energy which must be imparted in vibrating the entire system. Decks of this size can typically employ vibration motors of 40 horsepower or more. Another disadvantage of such prior decks is their susceptibility to need frequent maintenance because of the substantial vibration imparted to the entire deck for sustained lengths of time.
Other screening devices have suffered from an inability to adjust the surface tension of the screening material. Various types of materials require different tensioning of the screening surface to provide maximum efficiency in separating and classifying solids and particulates. It is therefore an object of this invention to provide a means for adjusting the surface tension of the screening material.
Other screening apparatuses have been developed which attempt to reduce the substantial energy requirements. In these apparatuses, a plurality of smaller vibrators motors have been employed which are coupled to a tappet shaft extending beneath the screen material at various locations spaced along the length of the screen. The tappet shaft is coupled by relatively complex linkages to the vibrator motor on the exterior of the frame of the deck. A plurality of tappet arms are positioned on the shaft which move eccentrically to tap the screen from beneath. In such prior screening decks only the screen is vibrated rather than the entire frame and thus the energy consumption is reduced. The particular tappet arrangements in such decks necessitate relatively complex linkages and cause localized tapping of screen both of which result in concentrated wear. Such prior screening decks require frequent adjustment to keep the screen in contact with the tappets. Such prior screening decks are also subject to blinding problems. It is therefore an object of this invention to eliminate these complex linkages and frequent necessity for adjustment.